Current Guidelines for Infective Endocarditis Prophylaxis

Infective endocarditis is an uncommon condition associated with significant morbidity and mortality. The practice of antibiotic prophylaxis which was introduced in 1955 by the American Heart Association guidelines and later adopted by Australia among other countries is based on the rationale that the condition arises from bacteraemia induced by certain invasive dental and medical interventional procedures in patients with a predisposing cardiac lesion, and that prophylactic antibiotics given empirically would destroy circulating bacteria and thus prevent the development of vegetations on susceptible endocardium1.

The aims of these clinical guidelines are to identify the groups of patients that are considered at risk of infective endocarditis, the procedures for which prophylaxis may be considered, and to recommend an appropriate antibiotic regime. Until recently there have been few changes in these recommendations over time other than variations in the antibiotic choice and route of administration, and simplification of dosing regime2.

The advent of evidence based medicine and systematic reviews has led to major revisions of these clinical guidelines in the past three years. Guidelines recommended by the 2006 British Society for Antimicrobial Chemotherapy and the 2007 American Heart Association have highlighted the paucity of primary data regarding the question of effectiveness of antibiotic prophylaxis before invasive dental and medical procedures in preventing disease occurrence in people at high risk of endocarditis. The British guidelines3 reduced the categories of cardiac conditions requiring antibiotic prophylaxis to patients with a past history of infective endocarditis, prosthetic valves and some specific congenital heart diseases. The American guidelines4 include similar categories and in addition cardiac transplant recipients with valvulopathy. The more recent 2008 UK Department of Health guideline5 developed by the National Institute for Health and Clinical Excellence (NICE) is an even more radical departure from earlier guidelines in that it recommends antibiotic prophylaxis used solely to prevent infective endocarditis not be given to patients, regardless of their risk status, undergoing dental and invasive medical procedures.

The recently updated Australian Therapeutic Guidelines for the use of antibiotics for prophylaxis against infective endocarditis have followed the lead of the American Heart Association and continued to reduce the number of categories of patients for whom prophylaxis is recommended. The Australian guidelines differ from the American and UK guidelines in two specific ways: prophylaxis is recommended in indigenous Australians with rheumatic heart disease, and there is a clear description of dental procedures for which antibiotics prophylaxis are required for at risk cardiac patients.

The 2008 Australian guidelines recommend antibiotic prophylaxis only for patients with the following cardiac conditions which are thought to be associated with the highest risk of adverse outcomes from endocarditis if undergoing a specified dental or medical procedure6 :

Cardiac transplantation with the subsequent development of cardiac valvulopathy

Congenital heart disease but only if it involves:

Unrepaired cyanotic defects, including palliative shunts and conduits

Completely repaired defects with prosthetic material or devices whether placed by surgery or catheter intervention, during the first 6 months after the procedure (after which the prosthetic material is likely to have been endothelialised)

Repaired defects with residual defects at or adjacent to the site of a prosthetic patch or device (which inhibit endothelialisation

The following antibiotic regime is recommended for standard prophylaxis7:

Amoxycillin 2g orally (in a child 50mg/kg up to 2g) 1 hr before procedure, or

Amoxycillin/ampicillin 2g IV (in a child 50mg/kg up to 2g) just before, or IM 30mins before procedure

For patients hypersensitive to penicillin, or those on long-term penicillin therapy, or who have taken penicillin or a related beta-lactam more than once in the previous month:

Clindamycin 600mg (in a child 15mg/kg up to 600mg) orally 1 hr or IV just before (dental and respiratory) procedure or

Lincomycin 600mg (in a child 15mg/kg up to 600mg) IV before (dental and respiratory) procedure or

Vancomycin 25mg/kg up to 1.5g (30mg/kg up to 1.5g if less than 12yrs) IV infusion over at least 1 hr, ending the infusion just before the procedure or

Teicoplanin 400mg (in a child 10mg/kg up to 400mg) IV just before or IM 30mins before procedure or

Cephalexin 2g (in a child 50mg/kg up to 2g) orally 1 hr before the (dental or respiratory) procedure if the liquid form of clindamycin (which is not available in Australia) is required.

For patients who have a high risk cardiac condition undergoing procedures which involve incision and drainage of abscess or surgical incision of infected skin, antibiotic treatment should be given as recommended for the organ specific procedure as detailed in the Therapeutic Guidelines: Antibiotic version 13.

It has been acknowledged that the changes in recommendations may be confusing to patients who have been receiving prophylactic antibiotics over their lifetime and are unwilling to change this practice. Some medical and dental practitioners will also be resistant to change and will continue to prescribe antibiotic prophylaxis. The changes may be more of a slow evolution as both patients and clinicians come to appreciate the lack of evidence for a benefit of antibiotic prophylaxis8.

1 Prevention of Infective Endocarditis: Guidelines from the American Heart Association: A Guideline from the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee, Council on Cardiovascular Disease in the Young, and the Council on Clinical Cardiology, Council on Cardiovascular Surgery and Anesthesia, and the Quality of Care and Outcomes Research Interdisciplinary Working Group. Wilson W et al; Circulation 2007;116:1736-1754.

3 Guidelines for the prevention of endocarditis: report of the Working Party of the British Society for Antimicrobial Chemotherapy. Gould F et al; Journal of Antimicrobial Chemotherapy 2006;57:1035-1042.

4 Wilson W et al, above 1.

5 National Institute for Health and Clinical Excellence. Prophylaxis against infective endocarditis. Antimicrobial prophylaxis against infective endocarditis in adults and children undergoing interventional procedures. URL: ‘http://www.nice.org.uk./CG064’ accessed 22 July 2008.

Disclaimer:The purpose of this document is to provide general information regarding some aspects of cardiology for medical practitioners. The information contained in this document is of a general nature only and does not purport to take into account, or be relevant to, the circumstances of a particular patient. SA Heart and the author(s) of this document assume no responsibility whatsoever if all or any part of this information or advice is relied on, or acted upon, by any medical practitioner or any other member of the public. Medical practitioners and non medically qualified individuals should seek professional advice from suitably qualified cardiologists in relation to the diagnosis and treatment of cardiac conditions.